Question

lithium reacts spontaneously with bromine to produce lithium bromine. write the balanced chemical equation for the reaction. if 25.0g of lithium and 25.0g of bromine are present at the beginning of the reaction determine the excess reactant and the mass of the excess.

Answer 1

Answer: Li is the one in excess; 22.81 g Li

Step-by-step explanation:

First it forms lithium bromide

2 Li + Br2 --> 2LiBr

25 g Br2/160 g Br2 X (2moles Li /1mole Br2 ) X (7grams Li/1mole Li) = 2.19 g Li

25 g Li x ( 1mole Li/7 g Li) X ( 1 mole Br2/2 mole Li) x( 160 g Br2 / 1 mole Br2) = 285. 71 g Br2

Now you subtract starting with number given

so 25 g Li - 2.19 g Li = =22.81 g Li

25 g Br2 - 285.71 g Br2 = -260.71 g Br2 (negative means its the limiting reactant. + means its the one in excess)